The generation of random numbers is of substantial importance in cryptographic systems, whether for generating codes or for dynamizing encoding processes. The quality of a random number generator and thus also of the random numbers themselves is crucial for the security of the cryptographic processes. Put in simple terms, the quality of a random number generator is higher the less probable it is to predict a random number and the smaller the functional link is between the random numbers. The quality of a random number generator can be calculated by elaborate statistical methods, which shall not be dealt with here in any detail.
It has been known for some time to use a random number generator consisting of an algorithm that, starting from a start value and using a code, generates a number that has a random character in the case of high-quality algorithms. A random number generator of this type is known, for example, from U.S. Pat. No. 4,974,193 this generator being implemented in a data processing system comprising a so-called chip card and a terminal. The algorithm is provided in the processing unit (microprocessor) of the chip card, that also has the necessary storage modules. According to the proposals of EP 281 057 the start value is changed whenever a random number is generated. This variable start value can be gained from the output signal of a real-time clock module implemented in the integrated module, or from data stored in the chip. Since the start values are determined whenever random numbers are generated the time of their generation is known to an outsider. Thus making the information used as a start value fundamentally predictable, for example if the information is gained from the output signal of a clock module.
The invention is therefore based on the problem of further increasing the security requirements for the generation of random numbers compared to known methods.
This problem is solved by the features stated in the main claim.